1. Field of the Invention
The present invention relates in general to noise suppression of jet engines and relates in particular to the use of a flade nozzle for providing a relatively low velocity exhaust flowstream which surrounds the lower portion of the core engine exhaust flowstream.
2. Description of Prior Developments
High thrust jet engines are currently used to power high speed civil transport aircraft, sometimes referred to as supersonic transport aircraft. Unfortunately, high thrust jet engines generate high exhaust noise levels which are subject to governmental noise level limits. In order to operate within such limits, jet noise abatement techniques including both mechanical suppression and acoustical shielding have been developed.
Mechanical noise suppression requires the installation of additional mechanical components to the jet engine, thereby undesirably adding additional weight to the engine. Acoustical shields require the production of a relatively low velocity exhaust stream which surrounds the primary or core engine exhaust stream. Such low velocity exhaust streams can be produced by bleeding gas from the core engine main jet through choke plates to reduce exhaust velocity. Unfortunately, this approach detracts from the main propulsion system and can impose both weight and drag penalties.
Accordingly, a need exists for a noise suppression system for a high speed, high thrust jet engine which does not impose significant weight and drag penalties on the engine.